I’m a huge fan of Arduino, JeeNode, ESP8266. A few of them connected in a network is one of the best solutions to distribute sensors data, relays command and status, LCDs and so on. But what should we use for networking the nodes? Wifi is built into the ESP8266 so that’s a no-brainer. JeeNode has an RF12b working on 868Mhz, but what if you don’t want to use wireless? What if you want to use wired sensors and supply power to them over the same wire? I have looked at RS232 and Ethernet. RS232 is low cost but in its standard form best suited for point to point connections. Ethernet is much better, Ethernet Cards and libraries are easily available for the Arduino. Cost wise, it’s not the best solution, though.
A few years back I bought a small PV Solar system. Only 3 230Wp panels and a Soladin 600 inverter. I installed the system myself on the shed using Ubbink Consoles. These consoles are really nice. They are lightweight, so easy to get to the roof and rock solid once weighed down with some 30x30cm concrete tiles.
The Soladin 600 has a serial port available but it is in an RJ12 form package. Interfacing is super easy thanks to the Soladin Arduino library. Just add two resistors and the hardware side is sorted.
I had a JeeNode lying around and with the addition of an MX485 IC, the connection to the RS485 bus was also sorted. A few lines of code later and the PV data from the Soladin Inverter was transmitting on a 10-second interval on the RS485 bus.